Vtp Modes; Vtp Advertisements - Cisco Catalyst 3750 Software Configuration Manual

Chapter 11 Configuring VTP

VTP Modes

You can configure a supported switch to be in one of the VTP modes listed in
Table 11-1 VTP Modes
VTP Mode Description
VTP server In VTP server mode, you can create, modify, and delete VLANs, and specify other configuration
parameters (such as the VTP version) for the entire VTP domain. VTP servers advertise their VLAN
configurations to other switches in the same VTP domain and synchronize their VLAN configurations with
other switches based on advertisements received over trunk links.
In VTP server mode, VLAN configurations are saved in NVRAM. VTP server is the default mode.
VTP client A VTP client behaves like a VTP server and transmits and receives VTP updates on its trunks, but you
cannot create, change, or delete VLANs on a VTP client. VLANs are configured on another switch in the
domain that is in server mode.
In VTP client mode, VLAN configurations are not saved in NVRAM.
VTP transparent VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its
VLAN configuration and does not synchronize its VLAN configuration based on received advertisements.
However, in VTP version 2, transparent switches do forward VTP advertisements that they receive from
other switches from their trunk interfaces. You can create, modify, and delete VLANs on a switch in VTP
transparent mode. The switch must be in VTP transparent mode when you create extended-range VLANs.
See the
When the switch is in VTP transparent mode, the VTP and VLAN configurations are saved in NVRAM,
but they are not advertised to other switches. In this mode, VTP mode and domain name are saved in the
switch running configuration and you can save this information in the switch startup configuration file by
entering the copy running-config startup-config privileged EXEC command.

VTP Advertisements

Each switch in the VTP domain sends periodic global configuration advertisements from each trunk port
to a reserved multicast address. Neighboring switches receive these advertisements and update their VTP
and VLAN configurations as necessary.
Note Because trunk ports send and receive VTP advertisements, you must ensure that at least one trunk port
is configured on the switch and that this trunk port is connected to the trunk port of another switch.
Otherwise, the switch cannot receive any VTP advertisements. For more information on trunk ports, see
the
VTP advertisements distribute this global domain information:
•
•
•
•
•
78-15870-01
"Configuring Extended-Range VLANs" section on page
"Configuring VLAN Trunks" section on page
VTP domain name
VTP configuration revision number
Update identity and update timestamp
MD5 digest VLAN configuration, including maximum transmission unit (MTU) size for each
VLAN.
Frame format
10-12.
10-16.
Catalyst 3750 Metro Switch Software Configuration Guide
Understanding VTP
Table 11-1.
11-3